OpenAI held its first developer conference, DevDay, announcing GPT-4 Turbo with a 128K context window and sharply lower prices, the Assistants API for building agent-like apps, and APIs for DALL·E 3 and text-to-speech. It also introduced GPTs, custom versions of ChatGPT anyone can create for specific purposes, along with plans for a GPT Store, underscoring OpenAI's evolution into a platform company.